Is anyone pulling vacuum to the crankcase from the header or using an electric brake booster vacuum pump from an '86 seville? I'm curious what gains would come from either on our cars.

 

Bump. no takers

 

i have one on my 68 camaro

 

Are you trying to reduce backpressure in your exhaust by sucking exhaust gas into your crankcase? Or are you trying to reduce pressure in your crankcase by sucking crankcase vapors out into your exhaust?

 

No,you create a vacuum in the crankcase even at WOT. the checkvalve is unidirectional. The tube going into the collector is at about a 40 to 45 degree angle & approx.1/3 into flow. (think 7000 rpm with no wind) Probably an easy 5+hp doing it the exhaust method.(Drag recers have to be careful with some oilpumps that create vacuum , that they don't get too close to 20" or the oil gets pulled out of the bearings too fast They pick up about 5% on top of their normal HP with 15" of merc.

 

I want to be the first to name this mod as the CVGS (Crankcase Vacuum Gain System).
namwob, I have seen this and understand the concept.Interestingly none of our dedicated tuners have mentioned it or come up with a kit yet.

 

What is this a PVC valve bypas?

 

Its an emissions checkvalve, (suck no blow) like used on some '80's chryslers. Speedshops sell the peices as a "pan evac. kit" (CVGS) Yeah norm03s

 

I don't understand where the extra horsepower is supposed to come from. The crankcase is already connected to the rubber elbow between the air filter and the throttle body. This area always sees vacuum while the engine is running, more vacuum at higher RPM.

 

So how does the bypass valve stay open? vacuum. How does it close? no vacuum. At higher rpm shouldn't it stay open then? no. With the length of the entire exhaust beyond the tube you have negative pressure, but without an extremely long ram pipe ahead of the throttle body, you have not much more than wind. There is slight suction to the crackcase, but no usable vacuum.

 

Theoretically it improves ring sealing at WOT, when there isn't any vacuum and blowby could actually pressurize the crankcase (especially in forced-induction engines). At least that was why everyone in the old days ran it with their supercharged drag cars. Still widely used: http://store.summitracing.com/defaul...sp&N=%2D115780

 

I still don't follow your reasoning. What does the bypass valve have to do with the idea of connecting the crankcase and the exhaust?

The bypass valve is held closed by a spring. It is held open by vacuum. The source for that vacuum is NOT the elbow between the air filter and the throttle body. The source for that vacuum is (stock) the air between the supercharger and intake manifold.

Again, why do you want to connect the crankcase and the exhaust manifold?

 

Actually, the purpose of the check valve is to ensure that when crankcase vacuum is high it won't suck exhaust in. So when crankcase pressure=high and exhaust pressure=low, the valve will open to vent the crankcase. Nothing at all to do with the supercharger bypass valve of course.

The exhaust is only used as a convenient vacuum source (which is why the original poster talked of a vacuum pump) and I'm not sure how effective this would be on a full-exhaust street car. Remember these kits are made for open headers...